There is other better way to do it for better precession and accuracy..??

None of what you suggest here will make for better precision or accuracy. Multiplying an inaccurate value won't make it more accurate.

Getting the signal each and every time, at the exact time it is sent, is how you improve accuracy. Precision is rather meaningless in this context. Either you got the pulse or you didn't. There isn't any middle ground.

Converting what is essentially a digital signal to analog via a frequency-to-voltage chip and then converting it back to digital strikes me as being a very silly way to make a digital RPM meter. Much better is to:

1. Clean up the input pulse if necessary so that you get one (or more) well-defined pulse(s) per revolution (you would have to do this anyway if you use a frequency-to-voltage chip);

2. Feed the pulse into an Arduino pin that supports interrupts. In the ISR, record the time that the pulse occurred using a call to micros(), and calculate the time since the previous pulse. Then the RPM is just 60 divided by the interval (in seconds) between pulses.

Formal verification of safety-critical software, software development, and electronic design and prototyping. See http://www.eschertech.com. Please do not ask for unpaid help via PM, use the forum.

Converting what is essentially a digital signal to analog via a frequency-to-voltage chip and then converting it back to digital strikes me as being a very silly way to make a digital RPM meter. Much better is to:

1. Clean up the input pulse if necessary so that you get one (or more) well-defined pulse(s) per revolution (you would have to do this anyway of you use a frequency-to-voltage chip);

2. Feed the pulse into an Arduino pin that supports interrupts. In the ISR, record the time that the pulse occurred using a call to micros(), and calculate the time since the previous pulse. Then the RPM is just 60 divided by the interval (in seconds) between pulses.

You are right.. I even had the same thought in my mind that why convert frequency to voltage and feed arduino when arduino itself can take the frequency directly..

If you read my posts right from the beginning, you will notice thats what I wanted to do ..

I wanted to find the time gap between pulses and calculate the RPM...But I just couldn't get how to find the interval...

OK, I'll assume you are using an Arduino Uno. This can generate interrupt 0 on pin 2 and interrupt 1 on pin 3. I'll assume you are feeding the ignition pulse (cleaned up if necessary) to pin 2. Here is a sketch to calculate the rpm:

have a Arduino duemilanove with the Atmega328.. Hope it will also able to take interrupts as the uno on the same pins.. as the uno also uses the 328...

As far as software code and hardware pin numbers there is no difference between Uno and your board. Only difference for Uno is smaller size bootloader that also uploads at a faster baudrate, everthing else is the same.

OK, I'll assume you are using an Arduino Uno. This can generate interrupt 0 on pin 2 and interrupt 1 on pin 3. I'll assume you are feeding the ignition pulse (cleaned up if necessary) to pin 2. Here is a sketch to calculate the rpm:

void loop(){ // insert code here to show the RPM on the display and delay for e.g. 0.2 seconds}

I've included some pulse cleanup in the software (i.e. ignore pulses that are less than 2ms apart).

@ dc42

First tell me how do I setup my hardware portion of pulse input to the arduino board..??I thought of using something like this http://www.sportdevices.com/rpm_readings/index.htmor tell me if there is any other way to pickup and feed the pulse which will just match your coding..

I went through your code, its just what I want to do, but couldnt plot out how to do it as I am not much advance in coding..

will you please make me understand this part... rpm = 60000000UL/(interval * pulsesPerRev); what is that 60000000UL...??